Sheet material such as that used in corrugated box construction is typically discharged single file and along a plane from a finishing machine in which the sheets are printed (with fast drying inks), shaped, creased, perforated or otherwise treated by the finishing machine. The sheets may be rectangular or of other configurations, but are typically flat and unfolded when leaving the finishing machine as shown at A in FIG. 1 of the drawings.
Forming rails and glue application heads are typically used downstream of the finishing machine to form the sheet material into desired configurations as they move along. A typical configuration is a partially folded box B, the folding process for which is exemplified in FIG. 1 of the drawings.
In existing technology, the boxes are counted and accumulated in bundles by a counter-ejector machine. This is an area where difficulty is experienced, since the boxes being fed along a plane, in end-to-end relation often have a tendency to re-open at the glue lines (see G in FIG. 1) as they leave the folding rails. If a glue line re-opens, the loose flaps F can cause frustrating and costly down-time while the single box is pulled from the counter-ejector.
Another problem with current feed systems for counter-ejectors is encountered when attempts are made to accumulate the boxes fed from a finishing machine, even if the glue joints hold. A finishing machine may operate to discharge partially folded boxes at a rate of up to 1000 feet per minute. The glue applicators and forming rails are capable of operating at a similar rate. However, it becomes difficult to effectively control accumulation of boxes into bundles at such a high feed rate.
One solution to the above problems is to slow down the box feed rate. This is an undesirable solution since the finishing machine should run at or near maximum efficiency, or the printing ink will dry and clog the printing heads.
Another solution to the above problem is to use hold-down devices on the glued boxes and to keep pressure on the glued joints until the glue cures. The problem with this solution is that the formed boxes are moving along at speeds up to approximately 1000 feet per minute. At this rate if the glue sets sufficiently in, say, 15 seconds, the distance from the glue applicator to the counter-ejector should be at least 250 feet. This is not acceptable either in terms of space limitations or in cost of equipment.
A still further problem comes with the nature of the hold-down devices in current use. Rollers have been used to press against the top surfaces of formed boxes as they move along, to hold the glued joints together. But rollers do not engage continuously and can catch a box edge, creating a jam in the machine. Another difficulty with rollers is that the surface contact sometimes causes damage to the engaged box surfaces.
An additional problem is realized when boxes of different dimensions are to be formed and collected. Adjustments must be made to accommodate the different box dimensions. This often takes a considerable amount of time and experimentation.
A still further problem occurs especially with counter-ejectors when stacking box blanks is required. The folded flaps on the boxes usually form a "tent" configuration, creating a difficulty for counter-ejectors to operate without occasional jams, especially as the boxes leave the feed conveyor and are accumulated in a counted stack on the ejector. This is due in large part to a lack of controlled engagement against the box flaps as the boxes leave the feed conveyor. The problem becomes exacerbated in situations where the glue has not completely set and the flaps become loose.
Loss of control also occurs at the point where the successive boxes are discharged from the feed conveyor to the counter-ejector machine. This is due in large part to the unpredictable nature of the partially folded boxes as they fall onto the stack. Guides have been developed to keep the stacks uniform, but little has been done to provide positive control of the boxes as they fall, especially at high feed rates.
Attempted solutions to this perplexing problem have usually involved some form of temporary intermediate support for the incoming boxes, to support the presently building stack while previously formed stacks are removed. Plates or fingers have been used for this purpose, moved into the path of descending boxes to provide temporary support.
Simply sliding a solid plate between falling boxes appears feasible, except that the speed at which the plate must move is prohibitive and dangerous. Further, a box edge is inevitably engaged and crushed by the leading edge of the fingers or plate.
Recognizing the above problems, the box stacking industry has resigned itself to slowing or stopping box infeed flow while formed stacks of the partially formed boxes are removed from below the stacker magazines. Unless slower drying ink is used, increased maintenance is experienced, especially at the printer area when ink dries in the printer machinery due to the stoppage.
From the above problems and inadequate solutions, it may be understood that need remains for a counter-ejector and feed system that can be placed in line with a box former, that will assure consistent and accurate feed of boxes and stacking in the counter-ejector regardless of the curing time required for the formed box joints, that will take up minimum floor space, and that will allow the associated finishing machine to run at efficient speeds. There is also a need for a counter-ejector with capability to accept and stack partially formed boxes. The present invention fills this need, as will be understood from the following description.